C# 避免为接口属性重复代码

Question

给定界面：

interface IVotable
{
    int TotalUpvotes { get; }
    int TotalDownvotes { get; }
    int TotalVoteScore { get; }
}

实施：

public class Comment : IVotable
{
    public int TotalUpvotes { get; private set; }
    public int TotalDownvotes { get; private set; }
    public int TotalVoteScore { get { return TotalUpvotes - TotalDownvotes + 1 ; } }
}

避免在每个 class 中以相同方式实施 TotalVoteScore 的最佳方法是什么？

Answer 1

如果你想要一个类似接口的东西（一个合同，说必须有一些方法具有指定的签名）结合通用代码，我想解决方案是一个抽象 class:

public abstract class Votable
{
    public abstract int TotalUpvotes { get; protected set; }
    public abstract int TotalDownvotes { get; protected set; }
    public virtual int TotalVoteScore { get { return TotalUpvotes - TotalDownvotes + 1; } }
}

并从中得出 class:

public class Comment : Votable
{
    public override int TotalUpvotes { get; protected set; }
    public override int TotalDownvotes { get; protected set; }
}

Answer 2

public abstract class VotableBase
{
    public int TotalUpvotes { get; protected set;}
    public int TotalDownvotes { get; protected set; }
    public int TotalVoteScore { get { return TotalUpvotes - TotalDownvotes + 1 ; } }
}

那么您的派生 class 不需要任何实现 - 它已经继承了属性：

public class Comment : VotableBase
{
    public void DoThings()
    {
        //e.g.
        Console.WriteLine(TotalVoteScore);
    }
}

Answer 3

如果 TotalVoteScore 始终以相同的方式计算，您可以将其作为 IVotable 上的扩展方法：

public static int TotalVoteScore(this IVotable v) {
    return v.TotalUpvotes - v.TotalDownvotes + 1
}

Answer 4

如果只是 TotalVoteScore 您不想重新实施，那么这就是要走的路：

public interface IVotable
{
    int TotalUpvotes { get; }
    int TotalDownvotes { get; }
    int TotalVoteScore { get; }
}

public abstract class VotableBase : IVotable
{
    public abstract int TotalUpvotes { get; protected set; }
    public abstract int TotalDownvotes { get; protected set; }
    public virtual int TotalVoteScore { get { return TotalUpvotes - TotalDownvotes + 1 ; } }
}

public class Comment : VotableBase
{
    public override int TotalUpvotes { get; protected set; }
    public override int TotalDownvotes { get; protected set; }
}

Answer 5

将构图方法融入其中。我一点也不反对继承。但这让我觉得这是一个不使用它的好例子。为什么要限制此 class 只能导出投票功能？我可以想象这个 class 有很多与 "Comment" 更密切相关的东西，例如作者信息（排名、个人简介、头像）、格式、年龄、编辑历史等。其中一些似乎可能更适合作为基础 class.

public interface IVotable
{
    int TotalUpvotes { get; }
    int TotalDownvotes { get; }
    int TotalVoteScore { get; }
}

// shared implementation
public class VoteStatus : IVotable
{
    public int TotalUpvotes { get; private set; }
    public int TotalDownvotes { get; private set; }
    public int TotalVoteScore { get { return TotalUpvotes - TotalDownvotes + 1; } }
}

// has A...
public class Comment : IVotable
{
    // expose it?
    public IVotable VoteStatus { get; private set; }

    // allow current vote status to be injected?
    public Comment(IVotable voteStatusReference)
    {
        this.VoteStatus = voteStatusReference;
    }

    // or don't use injection?
    public Comment()
        : this(new VoteStatus())
    {
    }

    public int TotalUpvotes => this.VoteStatus.TotalUpvotes;
    public int TotalDownvotes => this.VoteStatus.TotalDownvotes;
    public int TotalVoteScore => this.VoteStatus.TotalVoteScore;
}

注意：我也觉得这里的扩展方法建议比继承要好。

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